Spatial Ecology of the association between demosponges and Nemalecium lighti at Bonaire, Dutch Caribbean.

Coral reefs are known to be among the most diverse marine ecosystems and one of the richest in terms of associations and species interactions, especially involving invertebrates such as corals and sponges. The study of cryptofauna diversity associated with coral reefs is recently gaining momentum. There is an ever-growing body of scientific literature supporting the ecological importance that cryptofauna play in the survival and resilience of the reef ecosystem. Unfortunately, in the last decades, these associations have been threatened by climate change and anthropic pressure. Despite that, our knowledge about cryptic fauna remains remarkably scarce, therefore this study aimed to address this gap by defining for the first time the spatial ecology of the association between the epibiont hydrozoan Nemalecium lighti and the Porifera community of shallow coral reef systems at Bonaire. In particular, the host range, prevalence, and distribution of the association were examined in relation to different sites, depths, and dimensions of the sponge hosts. Nemalecium lighti has been found in association with 9 out 16 genera of sponges and 15 out 16 of the dive sites examined. The prevalence of the hydroid – sponge association in Bonaire reef was 6.55%, with maximum value of over 30%. This hydrozoan has been found to be a generalist symbiont, with a strong preference for sponges of the genus Aplysina and no significant preference in relation to depth. On the contrary, the size of the host resulted to influence the prevalence of association with large tubular sponges found to be the preferred host. Although further studies are needed to better explain the main biological and ecological reason for these results, this study improved our understanding about the cryptofauna diversity of coral reefs associations in Bonaire.